Computational simulation of slab vibration and horizontal-vertical coupling in a full-scale test bed subjected to 3D shaking at E-Defense

Abstract

This paper focuses on slab vibration and a horizontal-vertical coupling effect observed in a full-scale 5-story moment frame test bed building in 2 configurations: isolated with a hybrid combination of lead-rubber bearings and cross-linear (rolling) bearings, and fixed at the base. Median peak slab vibrations were amplified—relative to the peak vertical shake table accelerations—by factors ranging from 2 at the second floor to 7 at the roof, and horizontal floor accelerations were significantly amplified during 3D (combined horizontal and vertical) motions compared with 2D (horizontal only) motions of comparable input intensity. The experimentally observed slab accelerations and the horizontal-vertical coupling effect were simulated through a 3D model of the specimen using standard software and modeling assumptions. The floor system was modeled with frame elements for beams/girders and shell elements for floor slabs; the insertion point method with end joint offsets was used to represent the floor system composite behavior, and floor mass was finely distributed through element discretization. The coupling behavior was partially attributed to the asymmetry of the building that was intensified by asymmetrically configured supplemental mass at the roof. Horizontal-vertical coupled modes were identified through modal analysis and verified with evaluation of floor spectral peaks.